A subcutaneous device, such as a coil electrode for an implantable cardioverter-defibrillator (ICD), is typically implanted in a patient while the patient is lying supine on his or her back. The subcutaneous device is implanted using a tunneling tool that provides enough stiffness and pushability to create a space between the subcutaneous and muscular plane. With the patient on his or her back, it is difficult for a physician to maneuver a tunneling tool around the curvature of the posterior axilla to continue tunneling from the axilla to the spine.
There are two major potential problems that a physician may encounter while implanting a subcutaneous device using a tunneling tool. The first problem includes the tunneling tool turning inward between the ribs and into muscle and potentially creating a pneumothorax. The second problem includes the tunneling tool turning outward and potentially puncturing the skin. Some physicians will have a non-sterile scrub nurse put a hand under the patient's back to help guide the tunneling tool and to give the skin support so the tunneling tool does not penetrate the skin. Other physicians will use x-ray or other suitable imaging systems to help guide the tunneling tool.
For these and other reasons, there is a need for the present invention.
SUMMARY
One embodiment provides a system. The system includes a first electrode at a tip of a tunneling tool and a second electrode. The system includes a circuit configured to determine whether the tip of the tunneling tool is within subcutaneous fat tissue or muscle tissue of a patient based on a measurement of an impedance between the first electrode and the second electrode.